Mechanisms of Surfactant-Mediated Crystallization of Colloidal Quantum Dots

在化学系大分子、超分子和纳米化学（MSN）项目的支持下，哥伦比亚大学的Jonathan Owen教授正在研究控制纳米尺度晶体生长的基本过程。随着对晶体生长机制的深入了解，科学家们可以设计和制造性能更好的晶体，用于太阳能电池、发光二极管、激光器和能够在夜间捕获图像的红外相机。在这个项目中，晶体生长动力学是用同步加速器光源产生的X射线来监测的，这使得晶体形成的第一时刻可以可视化。发展了数学模型来描述生长晶体的演化和预测新材料的生长。欧文教授开发了一个教育计划，将研究与高中，本科和研究生研究人员的教育相结合，包括在纽约市学校为代表不足的小学，初中和高中学生提供服务的学生。该小组向公众宣传纳米材料研究的价值。在该项目中，使用原位光谱和X射线散射探测了硒化铅和硫化铅成核和生长的浓度和温度依赖性。真实的实时监控溶质浓度、粒度和产率。在成核阶段形成的中间体的原子结构原位探测使用对分布函数（PDF）分析的X射线散射。这些研究的补充，通过非原位研究的前体转化反应和生长动力学的大小依赖性，以达到一个整体的理解，每个耦合阶段的反应。速率方程模型和结构预测方法被用来模拟整个成核和生长过程中的溶质和纳米晶体的演变。欧文教授正在使用一种协同方法来帮助确定成核机制是否遵循经典过程，该过程涉及半径随过饱和度变化的临界核，特定“魔法大小”簇之间的速率限制过渡，从无定形中间体结晶，或分子过程。对晶体成核生长的更深入理解可以加速用于发光显示器、固态照明和光致发光的广泛的新材料的设计。欧文教授还与高中，本科和研究生密切合作，在这个项目上。他开发了一个实验室模块来教授高中生关于发光的知识，并与当地学校分享教学工具，这些学校为代表性不足的少数民族学生提供服务。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Macromolecular, Supramolecular, and Nanochemistry (MSN) Program in the Division of Chemistry, Professor Jonathan Owen at Columbia University is studying the fundamental processes that control the growth of nanometer scale crystals. With deeper understanding of crystal growth mechanisms, scientists can design and manufacture crystals with improved performance in solar cells, light emitting diodes, lasers, and infrared cameras capable of capturing images at night. In this project, crystal growth kinetics is monitored with X-rays generated at synchrotron light sources that allow the first moments of crystal formation to be visualized. Mathematical models are developed to describe the evolution of the growing crystals and predict the growth of new materials. Professor Owen develops an educational program that integrates the research with the education of high school, undergraduate and graduate student researchers, including students at New York City schools serving under-represented elementary, middle school, and high school students. The group communicates the value of research on nanoscale materials to the public.The concentration and temperature dependence of lead selenide and lead sulfide nucleation and growth is probed in this project using in situ optical spectroscopies and X-ray scattering. The solute concentration and the nanocrystal size and yield are monitored in real time. The atomic structure of intermediates formed during the nucleation phase is probed in situ using pair distribution function (PDF) analysis of X-ray scattering. These studies are complemented by ex situ studies of the precursor conversion reaction and the size dependence of the growth kinetics to arrive at a holistic understanding of each of the coupled phases of the reaction. Rate equation models and structure prediction methods are used to model the evolution of the solute and nanocrystals throughout nucleation and growth. Professor Owen is using a synergistic approach to help determine whether the nucleation mechanism follows a classical process involving a critical nucleus whose radius changes with the supersaturation, a rate limiting transition between specific “magic size” clusters, crystallization from an amorphous intermediate, or a molecular process. A deeper understanding of crystal nucleation growth can accelerate the design of a broad array of new materials for luminescent displays, solid state lighting, and photovoltaics. Professor Owen is also working with high school, undergraduate and graduate students closely on this project. He develops a laboratory module to teach high school students about luminescence and shares the teaching tools with local schools serving underrepresented minority students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.